- Short Workshop: Introduction to Meta-Analysis and Systematic Reviews June 25 – June 26,
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- Handbook of Meta-Analysis in Ecology and Evolution
Learn more. Increased implementation of these guidelines by authors, editors and publishers, and reinforcement by funders, will foster higher quality and more inclusive syntheses, further the goals of transparency and reproducibility in science, and improve the quality and value of primary research studies.
The sampling variance of the effect size expresses the precision with which the effect is estimated. These effect size measures can then be combined across studies, taking into account the precision with which each is estimated. One can then estimate an overall mean effect and confidence intervals around that mean effect, test whether the overall effect differs significantly from zero, assess whether the outcomes of the studies are heterogeneous, and if so, test hypothesized categorical or continuous covariates if any to account for that heterogeneity.
Moreover, ecological and environmental primary research is characterized by a diversity of model systems, geographical variability and stochasticity inherent to data collected under less controllable conditions, for example in the field. The number of relevant papers may vary strongly depending on the data sources, such as standard search engines e.
The number of studies found can be increased by using more keywords. To increase the likelihood of primary research studies being identified in a literature search, authors should carefully consider the choice of title, abstract content and keywords to find a balance between being broad enough to be found through a keyword search and being specific enough to be identified as relevant. If a publication cannot be made open access, many journals allow users to host a manuscript in an unedited form but permission depends on the policy and agreements established by the publisher. Online platforms, such as ResearchGate or Mendeley, substantially reduce the effort required for individual authors to provide full text access.
Effect sizes should summarize the results of each study on the same scale and in an unbiased manner. Data needed from each study to calculate effect sizes depend on the research question, the data structure and the specific metric of effect size chosen. The most commonly used effect sizes in ecology are standardized mean differences, response ratios and correlation coefficients using Fisher's Z transformation.
Response ratios and standardized mean differences are often used in ecological research syntheses when the goal is estimating the magnitude of the effect of an experimental treatment on a continuous response variable such as biomass. This is the case where one wishes to compare means for experimental and control groups from studies where means and standard deviations are reported. Ideally, raw data are provided. Study design should be clearly documented, including hierarchical designs and any aggregation of raw data e. It is essential to identify the measure of variation reported e.
In order to understand the outcome of a study, it is valuable to report or be able to calculate effect sizes and their variation. Therefore, another crucial step alongside the data extraction for calculation of effect sizes is the data extraction of relevant covariates moderators.
Variation in study outcomes may be due to biologically meaningful and important covariates organism traits, climate, population density, etc. Potential confounding of covariates must be directly discernible e. Detailed description of experimental methods and study design should include the number and sizes of sampling sites, plots within sampling sites, replicates within plots and study duration.
Description of study area should include exact geographical location as geographical coordinates or as a map as it may be needed for various reasons: First, to access regional climate data, general vegetation and other mapped data. To correctly match datasets on species occurrences and abundances from primary research studies authors must report species names according to a documented taxonomic authority e.
Grain denotes the size of the analytical unit. Focus is the area or inference space represented by each data point and thus represents the scale at which the grains are aggregated or the scale at which a mean is calculated. While grain is frequently reported, focus and extent are often missing or descriptions do not allow clear distinctions among the spatial scale components. Gewin It is critical to include sufficient metadata along with the archived data. The paper on the publisher's homepage should be always linked with this repository. However, researchers have an obligation to their funding and salary sources to report their results fully and accurately, and to the organisms and systems they study to make their results available to science.
As data reporting standards in primary research studies improve in the future, the need for data requests will likely diminish. Comprehensive reporting of results is important for understanding the primary research study and also facilitates future syntheses, as it will provide a more general understanding across different systems or experimental replicates.
This may be seen as an opportunity for primary research authors as it will increase study's transparency and clarity, and increase the options to use a study's data and findings, thereby increasing citations and broaden its impact. We estimate that the effort required to address these recommendations would not impose a major burden to the authors compared to the effort required to collect, analyse and publish the data. There are also implications for editors, publishers and funders.
To make the value of primary research longer lasting and have broader impact, journal editors, reviewers and publishers should provide published guidelines that require the listed information on the results of the study be included upon initial submission. Further, journals should require that data supporting the results in papers published in its journals will be archived in an appropriate public archive e. This is, however, highly controversial in the scientific publication world. Space limitations should not be a prohibitive factor in an era in which printed journals have become a rarity and data syntheses are increasingly essential.
Scientists need to acknowledge that each piece of research could be more than just a publication on a list; it could be an important part of a larger picture. KG and RS led the writing of the manuscript with the support of D. We thank Eduardo S. Santos and one anonymous referee for their valuable comments on the manuscript.
Volume 8 , Issue 6. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account.
If the address matches an existing account you will receive an email with instructions to retrieve your username. Methods in Ecology and Evolution Volume 8, Issue 6. Commentary Open Access. Katharina Gerstner Corresponding Author E-mail address: katharina. Holly P. Tools Request permission Export citation Add to favorites Track citation.
Short Workshop: Introduction to Meta-Analysis and Systematic Reviews June 25 – June 26,
Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Common problems found in primary research papers What to do? Why is this important? NGO reports, are difficult to find. Studies that are not indexed in major bibliographic databases will usually not be found or considerable effort is needed. Studies might be overlooked if title, abstract and keywords are too generic.
Consider your abstract and title to be distinctive from a review or opinion paper in the same field. In the title and abstract, use words that describe the main finding of the study, the geographical context, the methodology, and if possible the main covariates used in the analysis Relevant studies might not be identified and do not reveal that codable information is presented.
Studies might be overlooked if title and abstract are too specific, i. Consider possible broader questions, the findings might contribute to without overselling. Relevant studies might not be identified, as the presented findings might be seen as out of scope.
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Otherwise, respond timely to pdf requests. Ecological Statistics: Contemporary theory and application. Oxford University Press, Oxford, pp. Hillebrand, H. Meta-analysis results are unlikely to be biased by differences in variance and replication between ecological lab and field studies. Oikos Koricheva, J. Uses and misuses of meta-analysis in plant ecology. Journal of Ecology doi: Rollinson, Adam J. Laybourn, Tracy E. Scott, Matthew E.
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Aeillo-Lammens, Sarah M. Gray, James Mickley and Jessica Gurevitch. Biological invasions: a field synopsis, systematic review and database of the literature. Ecology and Evolution 3: DOI: Reporting standards in experimental studies. Editorial Ecology Letters Gurevitch, M. A Martins-Loucao, and C. C allocation to the fungus is not a cost to the plant in ectomycorrhizae. Conord, C. Fady and J. Large scale longitudinal gradients of genetic diversity: a meta-analysis across six phyla in the Mediterranean basin.
Handbook of Meta-Analysis in Ecology and Evolution
Ecology and Evolution 2: Fox, G. Wardle, Inderjit and D. Emergent insights from the synthesis of conceptual frameworks for biological invasions. Ecology Letters Gurevitch, J. A statistical view of research synthesis of patterns of species richness along productivity gradients: devils, forests and trees.
Ecology Invasions and plant competition. Simberloff and M. Rejmanek, eds. California Press, Berkeley CA. Howard, I. Ashton, E. Leger, K. Howe, E. Woo and M. Effects of experimental manipulation of light and nutrients on establishment of seedlings of native and invasive woody species in Long Island, NY forests. Biological Invasions Gurevitch , E. Woo, J.